In the petrochemical sector, corrosive products, such as hydrocarbons with a high sulphide and/or carbon dioxide content, are known to be conveyed along metal pipelines. In addition to good mechanical properties, the pipelines configured to convey corrosive products must have high resistance to corrosion; for said purpose, they have a metal wall covered by an inner coating which is made of metal alloys configured to withstand the corrosive agents and which is joined to the wall by cladding or by lining.
The pipelines clad or lined with the above-mentioned metal alloys are resistant to the aggressiveness of the corrosive products. However, the protection afforded by the cladding or lining is diminished when one end of the pipeline is joined to a tubular member.
The joint between a tubular member and the end of a pipeline is dictated, for example, by the need to connect the pipeline to a flanged connector adapted to repair a damaged pipeline.
A relatively simple method of joining a tubular member and a pipeline is described in European Patent No. 802,002 and PCT Patent Application No. WO 01/98701 and comprises the steps of inserting the end of the pipeline comprising an inner face, an outer face, and a front face, adjacent to the inner and outer faces, inside an inner seat of the tubular member, inserting an expandable mandrel inside the end of the pipeline, and expanding the expandable mandrel to join the end of the pipeline and the connector and eventually a forge member located therebetween.
The methods described above are not able to preserve the protection provided by the protective cladding/lining, even if the entire connector is made of corrosion-resistant material, because at least the front face of the pipeline is without the protective cladding/lining and, in use, could be, arranged in contact with the corrosive products. Furthermore, infiltrations of corrosive fluid could occur also along the portion of outer face adjacent to the front face.